Acute death in heartworm-infected cats: unraveling the puzzle

Litster, Annette, Atkins, Clarke and Atwell, Rick (2008) Acute death in heartworm-infected cats: unraveling the puzzle. Veterinary Parasitology, 158 3: 196-203. doi:10.1016/j.vetpar.2008.09.007


Author Litster, Annette
Atkins, Clarke
Atwell, Rick
Title Acute death in heartworm-infected cats: unraveling the puzzle
Journal name Veterinary Parasitology   Check publisher's open access policy
ISSN 0304-4017
1873-2550
Publication date 2008-12-10
Year available 2007
Sub-type Article (original research)
DOI 10.1016/j.vetpar.2008.09.007
Volume 158
Issue 3
Start page 196
End page 203
Total pages 8
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Subject 2405 Parasitology
3400 Veterinary
Formatted abstract
Although the acute death syndrome in feline heartworm disease is widely recognized, its pathogenesis remains a mystery. The most widely held hypothesis is that an acute anaphylactic reaction, perhaps precipitated by the death of the parasite, is the underlying cause. This study investigated the role of the physical form of antigen (Ag) in the ensuing reaction when Dirofilaria immitis-sensitized cats are challenged by intravenous (IV) administration of heartworm Ag. Healthy D. immitis-naive cats (n = 23) were sensitized using subcutaneous injections of adjuvanted D. immitis Ag administered weekly for 6 weeks. After sensitization, cats (n = 20) were anaesthetized and challenged with IV D. immitis Ag in various forms or with IV sterile 0.9% saline (n = 3). Systolic blood pressure, respiratory rate, degree of dyspnea, blood oxygen saturation, and heart rate were measured immediately before and at 10-15 min intervals after challenge until terminal apnea occurred or until euthanasia at 140 min after challenge. Blood samples were collected for complete blood count and measurements of serum serotonin immediately before and at 10, 20, and 35 min after challenge. Clinical observations were recorded as they occurred, or at 10-15 minute intervals, whichever was the more frequent. The most severe post-challenge reactions occurred in cats challenged with Ag from dead worms, live worms, and 20 ng/mL Ag. Dyspnea increased significantly after challenge in all three groups (p < 0.001; p = 0.04, and p = 0.002, respectively), and blood oxygen saturation dropped post-challenge in the Dead Worm (p < 0.001) and the 20 ng/mL Ag (p = 0.002) groups. In the 20 ng/mL Ag group, systolic blood pressure decreased (p < 0.05) and respiratory rate increased (p < 0.05) post-challenge. Clinical observations included dyspnea, gastrointestinal signs (retching, defecation, or flatulence), urination, and less commonly, hemorrhage from the nostrils or anus, or cutaneous swelling (general or specifically facial). The 20 ng/mL Ag group had the highest rate of clinical signs, followed by the Dead Worm group. The most common and reliable hematologic change associated with severe clinical effects of D. immitis Ag challenge was increased hematocrit, which was statistically higher after challenge than at baseline in the Dead Worm group (p = 0.012). The model demonstrated that the physical form of heartworm Ag used for IV challenge in D. immitis-sensitized cats is an important factor for determining the characteristics of the post-challenge reaction, and the amount of exposed internal filarial Ag presented to the feline immune system may influence the severity of the response to challenge.
Keyword Acute death
Cats
Dirofilaria immitis
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Special issue: "Heartworm Revisited: Selected papers presented at the 12th Triennial Heartworm Symposium 2007".

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Veterinary Science Publications
 
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